The Bush administration is expected to field two of its key players to testify on the political and non-proliferation aspects of the India-United States nuclear agreement before the powerful Senate Foreign Relations Committee, which will take up the landmark accord for a hearing on Thursday. Under Secretary of State for Political Affairs William Burns will be the main witness at the crucial hearing scheduled later in the day.

Coverage: The Nuclear Deal

John Rood, Acting Under Secretary of State for Arms Control and International security, is also expected to brief the Senate committee, sources said. Rood is to deal with the non-proliferation aspects of the Indo-US civilian nuclear agreement during the hearing, they said.

Burns will mainly focus on the political aspects of the historic accord, which the Bush administration hopes to conclude before September 26, when the Congress is scheduled to adjourn its final session before the November 4 presidential polls in the US.

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Rood, in a recent interview to the Financial Times, had rejected criticism that the Indo-US nuclear deal undermined efforts to crack down on proliferation.

"India is a growing power: they are going to play a bigger and bigger role on the world stage. If you are dealing with the challenge of, for example, Iran or Syria, it's far better to have the strong support of countries like India," said Rood, who spearheaded the US' effort to persuade countries in the 45-member Nuclear Suppliers' Group to permit nuclear trade with India early this month.

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The US congressional approval is now the last major hurdle before the nuclear deal can be operationalised.